Crystal and molecular structures of benzoylpyrenes and acetylpyrenes. E-, Z-, M- & P-stereodescriptors

The crystal and molecular structures of the following acetylpyrenes (AcPYs), and benzoylpyrenes (BzPYs) have been determined by X-ray crystallography: 1-acetylpyrene, 2-acetylpyrene, 1,3-diacetylpyrene, 1,6-diacetylpyrene, 1,8-diacetylpyrene, 2,7-diacetylpyrene, 1-benzoylpyrene (1-BzPY), 1,3-dibenzoylpyrene, 1,6-dibenzoylpyrene, 1,8-dibenzoylpyrene (1,8-Bz₂PY), 1-(4-fluorobenzoyl)pyrene, and 1,6-bis(4’-fluorobenzoyl)pyrene. Special attention was drawn to the stereodescriptors E, Z, P and M in the conformations of AcPYs and BzPYs. Geometrical parameters of the molecular structures of the AcPYs and BzPYs. and of previously reported crystal structures, including 1,3,6-tribenzoylpyrene and 1,3,6,8-tetrabenzoylpyrene are provided. Two cases of crystal dynamic isomerism, as distinct from polymorphism, have been revealed: 1E-BzPY/1/Z-BzPY and 1Z8E-Bz₂PY/1Z8Z-Bz₂PY. Most of the crystal structures of AcPYs and BzPYs under study adopt the more stable Z-conformations of the acetyl and benzoyl groups vis-à-vis the pyrene ring. The deviation from planarity of the carbonyl groups from the plane of the pyrene ring system is higher in AcPYs, as compared with BzPYs. The rich stereochemistry of the crystal structures of acetylpyrenes and benzoylpyrenes, as manifested in the E-, Z-, M- and P-stereodescriptors is noted.